When was the last time when serious new instrument was invented ?

How about: "Generally, the invention of truly novel instruments has slowed down since the 20th century. However, there are still interesting developments:

Recent inventions:

• The steelpan: This unique percussion instrument, born in Trinidad and Tobago in the early 20th century, is considered the only widely used acoustic instrument invented in that timeframe.
• Electronic instruments: The rise of electronic music in the 20th and 21st centuries has led to a constant stream of new electronic instruments, like the synthesizer, the sampler, and various digital controllers. These are constantly evolving and pushing the boundaries of sound creation.
• Experimental instruments: Many composers and musicians are constantly experimenting with new ways to create sound, pushing the boundaries of what constitutes a "musical instrument." These can be unique combinations of existing instruments, modified versions, or entirely new designs.

Factors to consider:

• Adoption and widespread use: While new instruments are constantly being invented, not all gain widespread adoption and become "serious" instruments in the traditional sense.
• Evolution of existing instruments: Many "new" instruments are often variations or adaptations of existing ones, making it harder to pinpoint a specific invention date."

Here are a few.

Jimi Hendrix kinda did. a few others helped too. but Jimi did the heavy lifting.

I’d say the most exciting thing on the music horizon is AI. Who hasn’t wished for an app that could build a song around a riff or a few bars hummed from your mouth?

I have a collection of fragments that have magically appeared in my head over the years. I’d say, at least enough for an album if I had the skills to build songs around them. They’re just sitting there on my digital recorder waiting for the AI app.

The fact they appear once-or-twice a year is why I never considered trying to "monetize" them. I’m sure Paul Simon, Peter Gabriel, etc. get these inspirations weekly at least.

Here's something new: